This invention relates to amplifiers and more particularly to compact amplifiers for use in automotive vehicles and other places where the limited amount of space and power available is an important consideration.
Emergency vehicles such as police cars, ambulances and the like require sirens that occupy a small amount of space but have a volume sufficient to be heard above normal ambient sound levels. Of course the amount of space available in any automotive vehicle is limited, as is the power available to run the siren. Numerous electronic sirens have been designed to meet these constraints, but generally they, and particularly their amplifiers, suffer from a variety of problems. Many units use a toroidal output transformer in the amplifier to obtain the desired efficiency, since toroidal transformers are inherently more efficient than other types of transformers. But toroidal transformers are expensive, particularly when compared with E/I lamination transformers. Moreover, toroidal transformers generally require output transistors that are beta-matched, which further increases the expense of the unit. Because of the limited space available, heat generation and heat dissipation are also significant problems in present units. In general, presently available units suffer from either high parts count or high heat dissipation or both in the amplifier. The first causes added expense while the second degrades the unit's performance.